Walrus

The walrus (Odobenus rosmarus) is a pinniped, or fin-footed MAMMAL (order CARNIVORA). It is the only member of the family Odobenidae, the name of which comes from the Greek words for "tooth" and "walks" in reference to walrus using their tusks to help haul themselves onto the ice. There are 2 subspecies: Pacific walrus (O.r. divergens) and Atlantic walrus (O.r. rosmarus); only the Atlantic walrus occurs in Canada. The former subspecies (O.r. laptevi) found in the Laptev Sea, Russia, is now considered to be Pacific walrus.

Description

Atlantic walrus adult females average about 275 cm in length and weigh approximately 850 kg. Average males are roughly 300 cm long and about 1000 kg. Some individuals are larger. There is regional variation in size; walrus from HUDSON BAY are smaller than others. Pacific walrus were thought to be larger but are similar in size to Atlantic walrus from some areas. The elephant SEAL is the only larger pinniped.

The walrus has a massive body with a large neck and disproportionately small head. The skin is thick, with many folds and creases, and with a sparse coat of coarse hair. Skin colour ranges from cinnamon to grey with pink in the folds and on the abdomen, and varies with skin temperature and related changes in blood flow; for example, walrus' basking in the sun causes their skin to become pink. Beneath the walrus's skin is a layer of blubber, about 6 cm thick. The feet are flippers and the hind feet can be turned forward for movement ashore. Both sexes have enlarged upper canine teeth, which form tusks up to 60 cm long. The stiff whiskers covering the muzzle are mobile and highly tactile.

Distribution and Habitat
Atlantic walrus range from central Canada to the Kara Sea, Russia. Pacific walrus occur from the eastern Kara Sea to Alaska. In Canada, walrus used to occur as far south as Nova Scotia but now the southern limits are generally JAMES BAY and the Labrador coast.

The walrus is often associated with the edges of SEA ICE in Arctic seas. In winter, they gather in polynias and in summer they haul out onto ice and land to rest and bask. Although walrus are capable of deeper dives, most feeding is done in waters less than 100 m deep. Their main prey are bottom-dwelling invertebrates, primarily bivalve MOLLUSCS. Some also kill and scavenge seals. CLIMATE CHANGE may alter walrus distribution through changes in sea ice or prey distribution.

Walrus are dispersed over a wide area within which they are normally found in groups of a few to hundreds of individuals. These 2 features make estimating population size difficult.

Reproduction and Development
Most females attain sexual maturity between 5 and 10 years of age and males between 7 and 14 years. Breeding is polygamous, with single large bulls attending groups of 5-20 or more females. Young, physically mature males may have limited breeding opportunities due to this social structure. Mating occurs between December and March. Implantation is delayed until June-July with most births in mid-April to June. Calves may nurse for 3 years although they may also take some solid food. Calves may be produced in alternate years, but more usually at 3-year intervals. POLAR BEARS and humans are the main predators on walrus.

Relationship with Humans
The large herds of walrus Jacques CARTIER discovered on Sable and Cape Breton islands and on the Îles de la Madeleine in 1534 were extirpated in the 16th and 17th centuries. In fact, between 1650 and 1850, European whalers almost exterminated the walrus in both the eastern and western Arctic.

Walrus are taken by the INUIT annually for subsistence purposes, and the walrus remains important to the Inuit for food, dog food and ivory, in addition to its cultural importance. There are 7 walrus stocks or management units in Arctic Canada. Two are shared with Greenland.

Author ROBERT E.A. STEWART

Links to Other Sites
Canadian Biodiversity Website
A great information source for all budding biologists. Learn about biodiversity theory, natural history, and conservation issues. From McGill’s Redpath Museum.

Hinterland Who's Who
Check out the extensive "Hinterland Who's Who" website for illustrated "Species Fact Sheets" about mammals, birds, reptiles, amphibians, and insects found in Canada. Also covers related conservation and biodiversity issues and includes related multimedia and educational resources. From the Canadian Wildlife Service and the Canadian Wildlife Federation.

Walrus
View a photo gallery and brief description of the walrus, Odobenus rosmarus. From the Canadian Museum of Nature.

Walrus
A fact sheet for that whiskered animal, the walrus. From the Canadian Geographic website.

Grace under water
This feature focuses on the biology and natural history of the walrus, Odobenus rosmarus. From the Canadian Geographic magazine.

Walrus, Odobenus rosmarus
Information about the natural history of the walrus, Odobenus rosmarus. From the University of Guelph.

Atlantic Walrus
An extensively detailed report on Atlantic walrus populations in Canada. From the Committee on the Status of Endangered Wildlife in Canada.

Arctic Mission
The website for Arctic Mission, a scientific voyage through the Arctic’s fabled North-West Passage. Features interactive maps, videos, photos and written observations about the landscape, climate, and wildlife that inhabit this region. From the National Film Board.

Walrus attacks on spectacled eider ducks caught on film
A BBC News article about walrus behaviour.